Facebook is an American for-profit corporation and online social media and social networking service based in Menlo Park, California.

The Facebook website was launched on February 4, 2004, by Mark Zuckerberg, along with fellow Harvard College students and roommates, Eduardo Saverin, Andrew McCollum, Dustin Moskovitz, and Chris Hughes.

YouTube is an American video-sharing website headquartered in San Bruno, California.

The service was created by three former PayPal employees—Chad Hurley, Steve Chen, and Jawed Karim—in February 2005.

Google bought the site in November 2006 for US$1.65 billion; YouTube now operates as one of Google's subsidiaries.

The site allows users to upload, view, rate, share, add to favorites, report and comment on videos, subscribe to other users, and it makes use of WebM, H.264/MPEG-4 AVC, and Adobe Flash Video technology to display a wide variety of user-generated and corporate media videos.

Available content includes video clips, TV show clips, music videos, short and documentary films, audio recordings, movie trailers and other content such as video blogging, short original videos, and educational videos.

Instagram is a mobile photo-sharing application and service that allows users to share pictures and videos either publicly or privately on the service, as well as through a variety of other social networking platforms, such as Facebook, Twitter, Tumblr, and Flickr.

Originally, a distinctive feature was its confining of photos to a square, similar to Kodak Instamatic and Polaroid SX-70 images, in contrast to the 4:3 aspect ratio typically used by mobile-device cameras.

In August 2015, version 7.5 was released for mobile devices, allowing users to upload media captured in any aspect ratio, but not at full size.

Users can also apply various digital filters to their images.

In June 2013, Instagram added support for videos, allowing prerecorded square standard definition resolution clips of up to 15 seconds to be shared; later updates introduced support for widescreen resolutions at 360p and longer recording times for either pre-recorded (up to one minute per video, or up to 10 minutes with a multi-video post) or disappearing live videos (up to one hour).

MPEG-1 and/or MPEG-2 Audio Layer III, more commonly referred to as MP3 (or mp3), is an audio coding format for digital audio which uses a form of lossy data compression, which are data encoding methods that use inexact approximations and partial data discarding to reduce file sizes significantly, typically by a factor of 10, in comparison with a CD, yet still sound like the original uncompressed audio to most listeners.

Compared to CD quality digital audio, MP3 compression commonly achieves 75 to 95% reduction in size.

MP3 files are thus 1/4 to 1/20 the size of the original digital audio stream.

This is important for both transmission and storage concerns.

The basis for such comparison is the CD digital audio format which requires 1411200 bit/s.

A commonly used MP3 encoding setting is CBR 128 kbit/s resulting in file size 1/11 (=9% or 91% compression) of the original CD-quality file.

Transcoding is the direct analog-to-analog or digital-to-digital conversion of one encoding to another, such as for movie data files (e.g., PAL, SECAM, NTSC), audio files (e.g., MP3, WAV), or character encoding (e.g., UTF-8, ISO/IEC 8859).

This is usually done in cases where a target device (or workflow) does not support the format or has limited storage capacity that mandates a reduced file size, or to convert incompatible or obsolete data to a better-supported or modern format.